This is a handlebar with an integrated pea shooter on the left side (for countries with right lane traffic orientation). The handlebar serves as the pea reservoir as well as a barrel. A spring-operated mechanism can be loaded and released with a small double-lever, very much like an index shifter.
On release, the pea shoots about 1 m to the left. A motorist overtaking you at a less than safe distance will hear the annoying impact of either actual dry peas or, for the more confrontational cyclist, little steel balls. Next time they will respect your personal space - or hit you directly.-- Toto Anders, Jun 09 2015random, halfbakery